- #1
wildman
- 31
- 4
I am looking at Palm's "Introduction to MatLab 7 for Engineers" page 511. The problem involves solving a Second Order Diff Equation. The solution to the diff equation is straight forward. What I am wondering is what Plam is doing in the plot function?
[tex] \ddot{\Theta} + \frac {g} {l} sin \Theta = 0 [/tex]
His answer is below:
in the m file pendul:
function xdot = pendul(t,x)
global g L
xdot = [x(2); -(g/L)*sin(x(1))];
in the m file example8_6_1
global g L
g = 9.81;
L = 1;
[ta, xa] = ode('pendul', [0,5], [0.5,0]);
plot(ta,xa(:,1), xlabel('Time (s)'), ylabel('Angle(rad)')
Question:
In the plot(ta,xa(:,1) what is the (:,1)? What is he doing? And why couldn't he just put an xa without the (:,1)?
[tex] \ddot{\Theta} + \frac {g} {l} sin \Theta = 0 [/tex]
His answer is below:
in the m file pendul:
function xdot = pendul(t,x)
global g L
xdot = [x(2); -(g/L)*sin(x(1))];
in the m file example8_6_1
global g L
g = 9.81;
L = 1;
[ta, xa] = ode('pendul', [0,5], [0.5,0]);
plot(ta,xa(:,1), xlabel('Time (s)'), ylabel('Angle(rad)')
Question:
In the plot(ta,xa(:,1) what is the (:,1)? What is he doing? And why couldn't he just put an xa without the (:,1)?